Denver GPS Base Station Upgrades Accuracy, Adds Real-Time Capability

Centennial, Colo., 12 September 2006 – The GPS correction data that has been available for free to users in the Colorado Front Range for the past eight years just got a lot more accurate. CompassTools Inc., the provider of GIS field data collection tools that established the GPS base station in 1998, has joined with Trimble and the University of Denver in upgrading the system to provide centimeter-level accuracy and real-time correction broadcasts.

“This base station is a great example of how industry and academia can cooperate to offer an enormous benefit to the surrounding community,” said CompassTools Inc. CEO W. Brant Howard.

JD Main, CompassTools Base Station Manager, added, “Survey-grade GPS users can now use the base station for centimeter-level postprocessing, while our sub-meter GPS users can enjoy the benefits of Internet-broadcast RTCM for real-time correction while they work in the field.”

Thousands of GPS receivers are used throughout Colorado by surveyors, civil engineers, researchers and natural resource managers. The accuracy of these devices, however, is normally only about 10 meters due to atmospheric signal degradation. To improve their accuracy, GPS users can obtain differential correction from a second receiver, known as a base station. The base station established by CompassTools on the University of Denver (DU) campus provides this correction data, which users can download for free at

The DU facility received a significant upgrade this summer when Trimble, the leading provider of GPS equipment and software, provided a geodetic-quality GPS receiver to serve as the new base station. The Trimble 5700 receiver includes a Zephyr dual-frequency antenna for improved signal reception and multi-path rejection, both of which improve GPS location accuracy. The enhanced equipment also enables the DU base station to broadcast correction signals in real-time over the Internet so users can correct their GPS location data as it is collected in the field.

“The Trimble 5700 is in a static location and provides a rock solid phase center for differential correction,” said Main. “This is the best free base station in Colorado.”

As it has for the past eight years, the DU Geography Department will continue to host the base station and its antenna on Boettcher Hall. CompassTools will make the correction data available on its web site. Dual-frequency correction data are collected every five seconds by the base station and posted as files on the web site every hour. GPS users up to 200 miles from Denver should be able to utilize the correction data.

About CompassTools Inc.
CompassTools Inc. is a one-stop shop for GIS field data collection equipment, software, consulting and services. Designed to assist clients in building their geographic information systems quickly and accurately, CompassTools carries all of the gear and software needed to develop a complete GIS, including mapping layers. Whether a client needs GPS receivers and data collection devices to conduct its own mapping or the right software to display and analyze data, CompassTools has the solution. CompassTools is a licensed reseller of products for Trimble, ESRI, Laser Technology, Ricoh, LizardTech, GeoSpatial Experts, Juniper Systems, GeoSpatial Innovations, Spatial Data, Red Hen Systems Inc., GeoEye, and several providers of aerial photography. Visit